The era of wireless communications is expanding at an unprecedented rate with the introduction of PCS (Personal Communication System) devices into the consumer market. The key issues involved in designing wireless systems are (i) integrating the digital base band subsystem with a high frequency analogue front end, and (ii) ensuring low voltage/power.
Presently, the majority of RC integrated circuits (IC's) are implemented using GaAs and bipolar technology, whereas the base band subsystems are implemented using CMOS technology. A significant amount of research is being expended towards developing RF IC's using CMOS technology (see A. N. Karanicolas, "A2.7V 900 MHz LNA and mixer," Proc. IEEE Inter. Solid-State Circuits Conference, 1996 and A. Rofourgaran, J. Y. C. Chang, M. Rofougaran, and A. A. Abidi, "A IGHz CMOS RF front-end IC for a direct-conversion wireless receiver," IEEE J. of Solid State Circuits, vol. 31, no. 7, pp. 880-889, July 1996).
Many of the recently developed CMOS circuits have the ability of operating with voltages as low as from 1.5 to 2.0 V. (see (1) D. K. Schaeffer and T. H. Lee, "A 1.5V, 1.5 GHz CMOS low noise amplifier," IEEE J. of Solid State Circuits, vol. 32, no. 5, pp. 745-759, May 1997; (2) P. J. Sullivan, B. A. Xavier and W. H. Ku, "Low voltage performance of a microwave CMOS Gilbert cell mixer," IEEE J. of Solid State Circuits, vol. 32, no. 7, pp. 1151-1155, July 1997; (3) B. Razavi, "A 1.5V 900 MHz down-conversion mixer," ISSCC Dig. Tech. Paper, February 1996, pp. 48-49; and (4) B. Razavi, "Design Considerations for Direct-Considerations for Direct-Conversion Receivers," IEEE Trans, on Circuits and Systems-II: Analog and Digital Signal Processing, vol. 44, no. 6, pp. 428-435, 1997).
Some effort has also been expended in the art to reduce the voltage supply for bipolar based technologies. In the work by Long, J. R. Lone and M. A. Copeland, "A 1.9 GHz low voltage silicon bipolar receiver front-end for wireless personal communications systems," IEEE J. of Solid State Circuits, vol. 30, no. 12, pp. 1428-1448, on-chip transformers are used to reduce the amount of DC head room required between the power rails.